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Updated: Nov 14 2022

Infantile Blount's Disease (tibia vara)

Images photo - courtesy Miller_moved.jpg diaphyseal angle_moved.jpg angle_moved.png
  • summary
    • Infantile Blount's disease is progressive pathologic genu varum centered at the tibia in children 2 to 5 years of age.
    • Diagnosis is suspected clinically with presence of a genu varum/flexion/internal rotation deformity and confirmed radiographically with an increased metaphyseal-diaphyseal angle.
    • Treatment ranges from bracing to surgery depending on patient age, severity of deformity, and presence of a physeal bar. 
  • Epidemiology 
    • Risk factors
      • overweight children
      • early walkers (< 1 year)
      • Hispanic and African American
  • Etiology
    • Best divided into two distinct disease entities
      • Infantile Blount's(this topic)
        • pathologic genu varum in children 2 to 5 years of age
        • male > female
        • more common
        • bilateral in 50%
      • Adolescent Blount's
        • pathologic genu varum in children > 10 years of age
        • less common
        • less severe
        • more likely to be unilateral
    • Pathophysiology
      • likely multifactorial but related to mechanical overload in genetically susceptible individuals including
        • excessive medial pressure produces an osteochondrosis of the medial proximal tibial physis and epiphysis
          • osteochondrosis can progress to a physeal bar
  • Anatomy
    • Genu varum is a normal physiologic process in children
      • physiologic genu varum
        • genu varum (bowed legs) is normal in children less than 2 years
        • genu varum migrates to a neutral at ~ 14 months
        • continues on to a peak genu valgum (knocked knees) at ~ 3 years of age
        • genu valgum then migrates back to normal physiologic valgus at ~ 7 years of age
  • Classification
    • Langenskiold Classification
      • type I thru IV consist of increasing medial metaphyseal beaking and sloping
      • type V and VI have an epiphyseal-metaphyseal bony bridge (congenital bar across physis)
      • provides prognostic guidelines
      • Infantile versus Adolescent Blount's
      • Infantile Blounts
      • Adolescent Blounts
      • Age
      • 2-5yrs
      • >10yrs
      • Bilaterally
      • 50% bilateral
      • Usually unilateral
      • Risks
      • Early walking, large stature, obesity
      • Obesity
      • Classification
      • Langenskiold
      • No radiographic classification
      • Severity
      • More severe physeal/ epiphyseal disturbance
      • Less severe physeal/ epiphyseal disturbance
      • Bone Involvement
      • Proximal medial tibia physis, producing genu varus, flexion, internal rotation, AND may have compensatory distal femoral VALGUS
      • Proximal tibia physis, AND may have distal femoral VARUS and distal tibia valgus
      • Natural History
      • Self-limited - stage II and IV can exhibit spontaneous resolution
      • Progressive, never resolves spontaneously (thus bracing unlikely to work)
      • Treatment options
      • Bracing and surgery
      • Surgery only
  • Presentation
    • Physical exam
      • genu varum/flexion/internal rotation deformity
        • usually bilateral in infants
        • may exhibit positive 'cover-up test'
      • often associated with internal tibial torsion
      • leg length discrepancy
      • usually NO tenderness, restriction of motion, effusion
      • lateral thrust on walking
  • Imaging
    • Radiographs
      • views
        • ensure that patella are facing forwards for evaluation (commonly associated with internal tibial torsion)
      • findings suggestive of Blounts disease
        • varus focused at proximal tibia
        • severe deformity
        • asymmetric bowing
        • medial and posterior sloping of proximal tibial epiphysis
        • progressing deformity
        • sharp angular deformity
        • lateral thrust during gait
        • metaphyseal beaking
          • different than physiologic bowing which shows a symmetric flaring of the tibia and femur
      • measurements
        • metaphyseal-diaphyseal angle (Drennan)
          • angle between line connecting metaphyseal beaks and a line perpendicular to the longitudinal axis of the tibia
          • >16 ° is considered abnormal and has a 95% chance of progression
          • Drennan angles between 11-16° necessitate close observation for the progression of tibia vara
          • <10 ° has a 95% chance of natural resolution of the bowing
        • tibiofemoral angle
          • angle between the longitudinal axis of the femur and tibia
  • Differential 
    • The following conditions can also lead to pathologic genu varum
      • persistent physiological varus
      • osteogenesis imperfecta
      • MED
      • SED
      • metaphyseal dysostosis (Schmidt, Jansen)
      • focal fibrocartilaginous defect
      • thrombocytopenia absent radius
      • proximal tibia physeal injury (radiation, infection, trauma)
  • Treatment
    • Nonoperative
      • brace treatment with KAFO
        • indications
          • Stage I and II in children < 3 years
        • technique
          • bracing must continue for approximately 2 years for resolution of bony changes
        • outcomes
          • improved outcomes if unilateral
          • poor results associated with obesity and bilaterality
          • if successful, improvement should occur within 1 year
    • Operative
      • proximal tibia/fibula valgus osteotomy
        • overcome the varus/flexion/internal rotation deformity
        • indications
          • Stage I and II in children > 3 years
          • Stage III, IV, V, VI
          • age ≥ 4y (all stages)
          • failure of brace treatment
            • progressive deformity
          • metaphyseal-diaphyseal angles > 20 degrees
        • technique
          • perform osteotomy below tibial tubercle
          • staged procedures may be required for Stage IV, V, VI
          • epiphysiolysis required in stage V and VI
        • outcomes
          • risk of recurrence is significantly lessened if performed before 4 years of age
      • growth modulation
        • technique
          • tension band plate and screws
      • physeal bar resection
        • indication
          • at least 4y of growth remaining
        • technique
          • perform together with osteotomy
          • interpositional material is usually fat or PMMA
      • hemiplateau elevation
        • technique
          • may be performed together with osteotomy
  • Techniques
    • Proximal tibia/fibula valgus osteotomy
      • goals of correction
        • overcorrect into 10-15° of valgus because medial physeal growth abnormalities persist
        • distal segment is fixed in valgus, external rotation and lateral translation
      • technique
        • staples and plates function by increasing compression forces across the physis which slows longitudinal growth (Heuter-Volkmann principle)
        • temporary lateral physeal growth arrest with staples or plates can be used
          • increasing use for correction in younger patients
        • include a bar resection (epiphysiolysis) when a physeal bar is present (Langenskiold V and VI)
          • consider hemiepiphysiodesis if bar > 50%
        • medial tibial plateau elevation is required at time of osteotomy if significant depression is present
        • consider prophylactic anterior compartment fasciotomy
  • Complications
    • Compartment syndrome (with high tibial/fibular osteotomy)
      • prophylactic release of anterior compartment
    • Recurrence of tibial vara
      • severe cases of Infantile Blount's disease may develop a physeal bar
        • can result in progressive varus after a well executed proximal tibial valgus osteotomy
        • may require a lateral tibial hemiepiphysiodesis or bar resection
  • Prognosis
    • Best outcomes with early diagnosis and unloading of the medial joint with either bracing or an osteotomy
    • Young children with stage II and stage IV can have spontaneous correction
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